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United States Patent |
6,180,684
|
Halmo
,   et al.
|
January 30, 2001
|
Process and an integrated plant for the production of synfuel and
electrical power
Abstract
The present invention relates to a process and an integrated plant to be
used in the process for the preparation of synthetic fuel (synfuel) and
production of electrical energy. A part of the energy produced is used for
the operation of the energy requiring steps of the process, whereas the
residual part is exported for other purposes. The warm exhaust gas from
the part of the plant producing electrical energy is fed to a preheating
step for natural gas being used as a starting material for the preparation
of synfuel.
Inventors:
|
Halmo; Terje M. (Stavanger, NO);
Martinsen; Alf S. (Sandnes, NO);
Hansen; Roger (Trondheim, NO);
Schanke; Dag (Trondheim, NO)
|
Assignee:
|
Den Norske Stats Oljeselskap A.S. (Stavanger, NO)
|
Appl. No.:
|
341892 |
Filed:
|
September 3, 1999 |
PCT Filed:
|
January 23, 1998
|
PCT NO:
|
PCT/NO98/00023
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371 Date:
|
September 3, 1999
|
102(e) Date:
|
September 3, 1999
|
PCT PUB.NO.:
|
WO98/32817 |
PCT PUB. Date:
|
July 30, 1998 |
Foreign Application Priority Data
Current U.S. Class: |
518/705; 60/39.35; 60/670; 518/700; 518/703; 518/704 |
Intern'l Class: |
C07C 027/00; F01K 025/00; F02C 003/14 |
Field of Search: |
518/703,704,705,700
60/670,39.35
|
References Cited
U.S. Patent Documents
4594140 | Jun., 1986 | Cheng | 208/414.
|
4927856 | May., 1990 | Elion | 518/702.
|
5177114 | Jan., 1993 | van Dijk et al. | 518/703.
|
5472986 | Dec., 1995 | van Dijk | 518/705.
|
5635541 | Jun., 1997 | Smith et al. | 518/703.
|
Foreign Patent Documents |
179169 | Oct., 1992 | NO | .
|
Other References
International Search Report; PCT/NO98/00023; Jul. 7, 1998; Jack Hedlund.
"Industriell . . . naturgass"; Jan M. Overli; Institutt for termisk energi
og vannkraft at NTNU; 64168 Gassteknologi, chapter 6; see in particular p.
7.
WO 91/15446, corresponding to PCT/US91/02354, published Oct. 17, 1991.
|
Primary Examiner: Richter; Johann
Assistant Examiner: Parsa; J.
Attorney, Agent or Firm: Fish & Richardson P.C.
Parent Case Text
This application is a 371 of PCT/No. 98/00023 filed on Jan. 23, 1998.
Claims
What is claimed is:
1. A process for processing and converting a hydrocarbonous gas in an
integrated plant for the preparation of chemical reaction products and
mechanical and electrical power, wherein
a starting material comprising a first part of the hydrocarbonous gas is
fed to a plant for converting the starting material via carbon
monoxide-containing gas to a stream of converted products comprising a
major part of the chemical reaction products, and an exhaust gas stream
comprising a major part of unreacted amounts of carbon monoxide, hydrogen
or synthesis gas, residual amounts of low molecular products, steam,
carbon dioxide and inert components,
a second part of the hydrocarbonous gas and an oxygen-containing gas is fed
to a power station including at least one gas turbine for the production
of mechanical or electrical power for the operation of machinery in the
integrated plant and for export, and for the manufacture of a warm exhaust
gas, and wherein the exhaust gas from the at least one gas turbine of the
gas power station is supplied as a heat exchange medium at a temperature
of at least about 500.degree. C. to a prewarming step for heating the
starting material for the preparation of the carbon monoxide-containing
gas of the conversion plant.
2. The process of claim 1, wherein at least a part of the exhaust gas
stream from the conversion plant is supplied to the power station for
production of further amounts of power and warm exhaust gas.
3. The process of claim 1 or 2, wherein a third part of the hydrocarbonous
gas is fed to a gas processing plant wherein the hydrocarbonous gas, by
compression, cooling or rectification, is converted to single components
of the starting material, and wherein the required energy for this purpose
is supplied to the plant from the power station or a heat power station
connected to the conversion plant.
4. The process of claim 1, wherein carbondioxide in the hydrocarbonous gas
as fed to the gas processing plant is separated from the gas and used as a
part of the starting material for the preparation of conversion products
in the conversion plant.
5. The process of claim 1, wherein substantial amounts of components
present in the hydrocarbonous gas being fed to the gas processing plant
and which has a molecular weight which is higher than the molecular weight
of methane, is separated from the gas and used as part of starting
material for the preparation of conversion products in the conversion
plant.
6. The process of claim 1, wherein air is separated in an air separation
plant for the preparation of an oxygen rich gas stream which is reacted
with the heated starting material in the conversion plant for the
preparation of synthesis gas, and wherein the required amount of power for
this purpose is supplied to the plant from the power plant or a heat power
station, connected to the conversion plant.
7. The process of claim 1, wherein carbondioxide, which is present in the
exhaust gas stream from the converison plant, is separated from said gas
stream and supplied to the stream of starting material in the conversion
plant.
8. The process of claims 1, wherein the starting material which is fed to
the conversion plant is heated in a prewarming unit/furnace at a
temperature of at least 500.degree. C. and reacted with an oxygen
containing gas in a unit for the partial oxidation and reforming of the
starting material to a warm gas composition including hydrogen, carbon
monoxide, carbon dioxide, oxygen or nitrogen, whereupon
the resulting warm gas composition is passed through a heat recovering
unit, whereby a tempered gas composition having a temperature being lower
than 350.degree. C., is obtained,
the tempered gas composition is reacted in one or more reactors to chemical
reaction products and exhaust gas streams.
9. The process of claims 1, wherein the conversion plant manufactures a
synthesis gas composition being used as a starting material for the
preparation of Fischer-Tropsch products.
10. The process of claims 1, wherein a plant which is designed for
carbonylation or hydrocarbonylation of a starting material, is used as
conversion plant.
11. The process of claim 1, wherein a plant which is designed for the
manufacture of methanol or dimethyl ether, or compositions of methanol or
dimethyl ether, is used as the conversion plant.
12. The process of claims 1, wherein a part of the gas stream from the
conversion plant is recycled (via a conduit) to a previous step in the
process.
13. The process of claim 2, wherein carbon dioxide, which is either
recovered from the hydrocarbonous starting material which is fed to the
processing unit, or carbon dioxide being a part of the exhaust gas stream
from the conversion plant is recycled to the inlet stream of the
conversion plant.
14. The process of claim 2, wherein carbon monoxide recovered from the
carbon monoxide containing gas which is manufactured in the conversion
plant, and used for carbonylation of a starting material.
15. The process of claim 1, wherein heat power being released during
cooling of the warm gas composition, which is passed through the heat
recovery unit, is converted to further amounts of mechanical or electrical
power.
16. The process of claim 2, wherein compressed air for the preparation of
an oxygen rich gas composition to be used for oxidation of the carbonous
starting material in the conversion plant is withdrawn from an outlet of
an air compressor connected to a gas turbine of the power plant.
17. The process of claim 2, wherein the contents of NGL components are
reduced or eliminated from the first part of the hydrocarbonous gas, and
the thus obtained NGL depleted gas is used as a starting material for the
conversion to a carbon monoxide containing gas in the conversion plant,
the conversion of the NGL poor gas being effected by gas heated reforming.
18. An integrated plant for processing and converting a hydrocarbonous gas
in an integrated plant for the preparation of chemical reaction products
and mechanical or electrical power, wherein the integrated plant comprises
a plant for conversion of the starting material via carbon
monoxide-containing gas through a stream of conversion products,
comprising a major part of the chemical conversion products, and an
exhaust gas stream comprising a major part of the unreacted amounts of
carbon monoxide, hydrogen or synthesis gas, residual amounts or low
molecular products, steam, carbon dioxide and inert components, a power
plant including at least one gas turbine for the production of mechanical
or electrical power by reacting the starting material with an
oxygen-containing gas for the preparation machinery in the integrated
plant and for export, and for the manufacture of a warm exhaust, which is
used at a temperature of at least about 500.degree. C. as heat exchange
medium for the heating of the starting material for preparing the carbon
monoxide-containing gas in the conversion plant, having a connection
between the gas power plant including at least one gas turbine and the
preheating means, for transport of exhaust gas from the first mentioned to
the last mentioned, as well as heat exchange tubes in the last mentioned,
for converting heat from the exhaust gas to the hydrocarbonous gas being
preheated.
19. The plant of claim 18, characterized in an air separation plant for the
preparation of an oxygen-enriched gas stream as feed to the reforming
means for reforming the preheated natural gas from the preheating means
for converting heat from the exhaust gas to the natural gas being
preheated.
20. The plant of claim 18 or 19, wherein the preheating means is designed
for heating natural gas to at least 500.degree. C., the reforming means
being designed for partial oxidation and reforming of natural gas to a
warm gas composition including hydrogen, carbon monoxide, carbon dioxide,
oxygen or nitrogen, and the heat recovery unit is designed to provide a
tempered gas composition having a temperature below 350.degree. C.
21. The plant of claim 18, wherein the conversion plant is a plant for
carbonylation or hydrocarbonylation of natural gas.
22. The plant of claim 18, further comprising a gas processing plant for
the preparation of liquid single components, having a supplement of
required energy for this purpose from the power plant or a heat power
station connected to the conversion plant.
23. The process of claim 1, wherein the hydrocarbonous gas comprises
natural gas.
24. The process of claim 1, wherein the carbon monoxide-containing gas
comprises synthesis gas.
25. The process of claim 1, wherein the oxygen-containing gas comprises
air.
26. The process of claim 3, wherein the single components of the starting
material are in liquid form.
27. The process of claim 26, wherein the single components of the starting
material in liquid form comprise LNG.
28. The process of claim 6, wherein the oxygen rich gas stream is reacted
with the heated starting material and steam.
29. The process of claim 8, wherein the starting material is reacted with
the oxygen-containing gas and stream.
30. The plant of claim 18, wherein the hydrocarbonous gas comprises natural
gas.
31. The plant of claim 18, wherein the carbon monoxide-containing gas
comprises synthesis gas.
32. The plant of claim 18, wherein the power plant for production of
mechanical or electrical power reacts the starting material and the
exhaust gas stream from the gas conversion step with an oxygen-containing
gas.
33. The plant of claim 18, wherein the oxygen-containing gas comprises air.
34. The plant of claim 22, wherein the liquid single components comprise
LNG.
Description
The present invention relates to a processing and converting a
hydrocarbonous gas, particularly natural gas in an integrated plant for
the preparation of useful products, including chemical reaction products
and mechanical or electrical power, as well as an integrated process plant
for the accomplishment of such a process.
By the term <<hydrocarbonous gas>> in the present context and the appending
claims is understood hydrocarbon compositions consisting of hydrocarbon
components substantially existing in a gaseous form at standard pressure
and temperature conditions.
Natural gas is an important part of numerous petrochemical reservoirs and
can find utilization as starting materials for further refined products in
the form of pure hydrocarbons and in the form of oxidized derivatives
thereof. Further, natural gas can be used for the production of power such
as electrical power or mechanical power.
In many instances the natural gas reservoirs are situated at remote sites
from the established natural gas markets where the utilization thereof, as
mentioned above, takes place. This is e.g. the case in Europe, where the
petrochemical sources are situated at the sea bottom far away from the
European continent.
As a consequence thereof it will not be economical to transport the gas
through pipelines to the users, the pipeline systems being long and
expensive to install and later also to maintain.
For this reason the options of converting natural gas to other
transportable and useful products will be considered, such as e.g. synfuel
(synthetically prepared engine fuels in liquid form) and electrical power.
Depending on whether the further handling of the gas takes place at an
offshore production platform or at the site of entering the ground, it
is--provided that the further useful products are to be prepared at one
and the same geographical site--economical to evaluate the integration
benefits which may be achieved by a suitable connection of the various
kinds of plants for the abovementioned purposes.
Natural gas substantially consists of methane admixed with other gaseous
hydrocarbons, CO.sub.2 and gaseous sulphur compounds such as H.sub.2 S and
lower mercaptanes.
When the methane is preheated to a temperature of the order 800.degree. C.
and then is supplied with oxygen in a reforming step, oxygenated products
of the methane are formed primarily in the form of CO and H.sub.2. This
gas composition is called <<synthesis gas>>. Such a synthesis gas may
alternatively be prepared by reacting the hydrocarbonous material with
aqueous vapour under pressure and at high temperatures according to the
scheme:
CH.sub.4 +H.sub.2 O.fwdarw.CO+3H.sub.2.
When the synthesis gas is formed by partial oxidation, energy is released
in the form of heat. This heat may be recovered from this step and
optionally transferred to mechanical or electrical power.
The synthesis gas may then be reacted in a further step to methanol and
dimethyl ether or in a Fischer-Tropsch synthesis to straight alkanes
and/or alkenes of a higher molecular weight than the prevailing
hydrocarbons of the natural gas.
##STR1##
The products of the reaction step of carbon monoxide and hydrogen gas is
the product called <<synfuel>>(synthetic fuel) and being the intended
product of the process. The chemical composition of the product will
depend on the preparation method and the operation conditions. The term
synfuel thus covers products such as methanol, dimethyl ether, mixtures of
methanol and dimethyl ether, other oxygenates, Fischer-Tropsch
hydrocarbons and further processed products thereof, among others
lubricants which may be prepared from the heavier Fischer-Tropsch
hydrocarbonous fractions.
Furthermore, non-reacted gas and side products may be recovered as a
separate stream and may be recycled to the reforming step or used as fuel
for the production of power.
The conversion of synthesis gas is e.g. disclosed in G. A. Mills, <<Status
and opportunities for conversion of synthesis gas to liquid fuels>>, Fuel,
vol. 73(8) pp 1243-1279, (1994).
The Norwegian publication 179 169 discloses a process of converting natural
gas to a normally liquid, carbonous compound such as methanol and/or
dimethyl ether and/or liquid hydrocarbons of gasoline quality and/or
olefins. The process avoids requirement of vapor reforming and/or
adiabatic reforming of natural gas to synthesis gas using a substantially
pure oxygen. The synthesis gas may be prepared at an operative pressure
which is useful for converting the gas to methanol and/or dimethyl ether
without recompression of the synthesis gas. The exhaust gas from the
overhead has, subsequent to the conversion of the crude product
methanol/DME and/or conversion to liquid hydro-carbons of gasoline
quality, generally a BTU-capacity which is required for the use as fuel
gas for the power supply being required for the operation of the required
gas compression facilities used in the process. This renders the operation
of the plant more economical and a process useful at remote sites.
Particularly claim 4 of the publication for opposition states that air is
introduced in the compressor unit of the gas turbine, the residual gas
balance from the synfuel production including unreacted H.sub.2, CO and
methane, being introduced through the fuel entrance of the
<<expander-driver>> unit of the gas turbine as a fuel for this part of the
air from the outlet of compressed air from the gas turbine being lead to
the entrance of a gas compressor driven by the gas turbine for compressing
natural gas being introduced through the entrance to a gas compressor
operated by a gas turbine and compressed to an enhanced end-pressure, the
end-compressed air being heated to a higher temperature, the compressed
natural gas being heated to a high temperature, the compressed gases being
used in an adiabatic reaction yielding a reformed gas stream having a
temperature of 982-1371.degree. C.
U.S. Pat. No. 5,177,114 claims the same priority as the Norwegian
publication No. 179169 and does not appear to differ be substantially
therefrom.
U.S. Pat. No. 4,927,856 combines the production of electrical power,
hydrogen gas production and methanol in an integrated system and discloses
a corresponding process. The electricity is formed in turbines run by
heated gas from a pressurized fuel source, and the electricity is then
used in an electrolysis unit converting water, optionally condensed from
the source gas, to hydrogen gas which is subsequently reacted with
hydrocarbon oxides of the source gas under the formation of methanol.
U.S. Pat. No. 5,245,110 discloses the preparation of an oxygen enriched gas
composition in an apparatus comprising a gas turbine, an oxidation
separation plant in a fluid connection with the turbine air compressor and
means for maintaining an appropriate mass balance-tolerance between the
turbine compressor unit and the turbine power production unit.
In U.S. Pat. No. 5,284,878 methanol is produced by reacting a CO-rich
synthesis gas in the presence of a powder methanol synthesis catalyst
suspended in an inert aqueous phase reactor system. Unreacted CO-rich
synthesis gas is recycled to the reactor. Preferably the process is
integrated with a carbon gasification system for the production of
electrical power in which one part of the unreacted synthesis gas is used
as a fuel, and part of the methanol product is used as further fuel in
periods of an increased demand.
U.S. Pat. No. 4,296,350 discloses the production of mechanical and
electrical power combined with synthesis or fuel gas in a partial
oxidation process by integration combustion and steam turbines. The side
product evaporated prior to condensed natural gas is brought through
pipelines to the gas consumers. The conversion of the synthesis gas to
synfuel is not disclosed.
U.S. Pat. No. 4,359,871 discloses a process and an apparatus for the
cooling of natural gas.
When gas recovered from petrochemical reservoirs at the sea bottom in
arctic wafers is brought ashore to a land based plant, in arctic regions,
problems arise and conditions which are substantially distinguished from
the conditions under which the abovementioned prior art aims to solve the
problems.
The distance to the site of use is long and transport of gas through
pipelines to these will require immense investments and pipelines which
will be uneconomical.
Further, the sites of bringing ashore may be far away from suitable energy
sources which are required in the further processing of the natural gas
brought ashore.
These conditions result in particular problems which are therefore not
found to be solved through the prior art technique.
A maximum integration of such a plant is desirable which must
simultaneously produce products which are well suited for the transport in
a liquid form to a site of use.
This problem may be solved by a process as disclosed in the introduction
wherein
unreacted natural gas or other hydrocarbonous gas is fed to a plant for
converting the starting material via a hydrogen or carbon monoxide
containing gas, particularly a synthesis gas, to a stream of conversion
products comprising a major part of the chemical reaction products, and an
exhaust stream comprising a major part of unreacted amounts of carbon
monoxide, hydrogen or synthesis gas, residual amounts of low molecular
products, steam, carbondioxide and inert components,
unreacted starting materials and optionally the exhaust stream from the gas
conversion step are fused with an oxygen containing gas, preferably air,
and then fed to a power plant for the production of mechanical or
electrical power for the operation of the machinery of the integrated
plant and for export, and for the formation of a warm exhaust, and that at
least a part of the required amount of power for this purpose is fed to
the plant from the power plant or conversion plant, and the exhaust from
the gas power station is fed to the conversion plant as a heat exchange
medium for the preheating step for heating a natural gas starting material
for the preparation of the carbon monoxide containing gas.
A further preferred aspect of the process of the invention is the
separation of air in an air separation plant for the preparation of an
oxygen rich stream of gas which is reacted with the heated natural gas and
optionally steam in the conversion plant for the preparation of a warm
synthesis gas.
The required amount of energy for this aim is supplied to the air
separation plant from the gas power plant or conversion plant.
A further preferred aspect of the process of the invention is the
separation of carbon dioxide residing in the exhaust gas stream from the
conversion plant from said gas stream and the stream of natural gas
starting material is fed to the conversion plant.
A further preferred aspect is that the natural gas starting material being
fed to the conversion plant is heated in a preheating unit/furnace to a
temperature of at least 500.degree. C. and reached with an oxygenous gas
and optionally steam in a reforming reactor for the partial oxidation and
reforming of the starting material to a warm gas composition including
hydrogen, carbon monoxide, carbon dioxide, oxygen or nitrogen, whereupon
the resulting warm gas composition is passed through a heat recovering
unit, in which a tempered gas composition having a temperature being lower
than 350.degree. C. is obtained, and the tempered gas composition is
reacted in one or more reactors to chemical reaction products and exhaust
streams.
The last-mentioned reaction may be a reaction to e.g. the oxidized products
methanol and dimethyl ether or may be a Fischer-Tropsch reaction resulting
in alkanes or alkenes, or the reaction may also involve a further reaction
to more oxygenated products, e.g. a carbonylation of methanol to acetic
acid.
As a consequence thereof, a preferred embodiment may be the presence of a
synthesis gas composition in the reforming plant as a starting material
for the preparation of Fischer-Tropsch products.
As a consequence of the abovementioned, a plant designed for the
carbonylation and hydrocarbonylation of a suitable starting material can
be used.
A further aspect may be that part of the exhaust stream from the last step
of the conversion plant is recycled through a conduit to a previous step
of the process, e.g. that it is admixed with the preheated natural gas and
entering the reforming reactor with this. A preferred aspect is further
that carbon monoxide is recovered from the carbon monoxide containing gas
being produced in the conversion plant and is used for the carbonylation
of a suitable starting material.
It is further preferred that heat power being released by cooling of the
warn gas composition being passed through the heat recovery unit is
converted to further amounts of mechanical or electrical power.
Further it is preferred that compressed air for the preparation of an
oxygen rich gas composition being used for the oxidation of the natural
gas starting material of the conversion plant is taken from the outlet to
an air compressor which is connected to a gas turbine of the power plant.
Further, it is preferred that NGL-components (liquid components of the
natural gas) are reduced in amount or removed from the natural gas, and
the thus obtained NGL depleted natural gas is used as a starting material
for the conversion to a carbon monoxide containing gas in the conversion
plant, which conversion is performed by <<gas heated reforming>>.
Further, the present invention relates to an integrated plant for
processing and converting natural gas or other hydrocarbonous gas for the
preparation of useful products including chemical reaction products and
mechanical or electrical power, which integrated plant comprising:
a plant for converting the starting material via a carbon monoxide
containing gas, particularly a synthesis gas, to a stream of conversion
products comprising a major part of the chemical conversion products and
an exhaust stream, comprising a major part of unreacted amounts of carbon
monoxide, hydrogen or synthesis gas, residual amounts of low molecular
products, steam, carbon dioxide and inert components,
a power plant for the production of mechanical or electrical power by
reacting unreacted residues of the starting material and optionally the
exhaust gas stream from the gas conversion step with an oxygen containing
gas, preferably air, for the operation of machinery of the integrated
plant and for export, and for the production of a warm exhaust being used
as heat exchange medium for heating the starting material for the
production of the carbon monoxide containing gas of the conversion plant.
In this integrated plant a connection is made between the gas power plant
and the preheating means for the transport of exhaust gas from the first
mentioned to the last mentioned, as well as heat exchange tubes in the
last mentioned for an efficient transfer of heat from the exhaust gas to
the natural gas which is to be preheated.
Further, it is preferred that the plant comprises an air separation plant
for the preparation of an oxygen enriched gas stream for the feed to the
reforming reactor for reforming the preheated natural gas from the
preheating means.
It is preferred that the preheating means is designed for heating the
natural gas to at least 500.degree. C., that the reforming reactor is
designed for partial oxidation and reforming of the natural gas to a warm
gas composition including hydrogen, carbon monoxide, carbon dioxide,
oxygen or nitrogen, and the heat recovering unit is designed to provide
for a tempered gas composition having a temperature below 350.degree. C.
A further preferred embodiment of the conversion plant comprises a plant
for carbonylization or hydro carbonylization of natural gas.
In the following the invention is described with reference to the appending
figure showing an integrated plant for the production of synfuel and gas
power.
On the figure the fed amounts of natural gas and produced amounts of
product and energy on a yearly basis is indicated.
MW=megawatt
t=ton.
BRIEF DESCRIPTION OF THE DRAWINGS
A natural gas stream 8, which may include a supplement being passed through
a conduit 46 from a plant for the partial liquefaction of natural gas, is
passed to a prewarming unit 2 having a heat supply by exhaust gas at a
temperature above 600.degree. C. through a pipe 33 from a gas power plant
30 situated close by. The exhaust gas is passed in a unit 2 through a heat
exchange plant for efficient transfer of heat to the natural gas to be
heated. When required, a plant for further direct heating of the
prewarming unit may be provided. The exhaust gas is vented to the
atmosphere after the delivery of heat to the prewarming unit.
The prewarmed natural gas at a temperature of at least 600.degree. C. is
then passed through conduits 3 to a reforming reactor 4.
This reforming reactor is simultaneously fed oxygen enriched gas from an
air separator 20 which is again fed atmospheric air from the surroundings
to an inlet 21, the feed of the oxygen enriched gas is indicated by 22.
The reforming in the reforming reactor 4 is run under conditions which are
closer defined in:
I. Dybkjaer, <<Tubular reforming and autothermal reforming of natural
gas--an overview of available processes>>, Fuel Processing Technology Vol.
42, pp 85-107 (1995).
B. M. Tindall and M. A. Crews, <<Alternative technologies to steam-methane
reforming>>, (Hydrocarbon processing, 75, Nov 1995).
.ANG., Solbakken, <<Synthesis gas production>>, (Natural Gas Conversion pp
447-455, A. Holmen et al. (ed), Elsevier Publ. 1991).
The synthesis gas including molecular hydrogen and carbon monoxide as the
further desired reactants, but in admixture with oxygen, carbondioxide,
nitrogen and other unreacted natural gas components, is passed through the
pipe 5 to a heat recovery plant 6. About 400 MW may be recovered therefrom
on a yearly basis. This heat can be used for the production of power as
e.g. indicated by a steam turbine 17.
The cooled synthesis gas is then passed through a pipe 10 to a
Fischer-Tropsch synthesis plant 11. The Fischer-Tropsch reaction of the
Fischer-Tropsch synthesis plant will include a catalyst, e.g. a cobalt
catalyst which, in addition to cobalt, may include parts of rhenium and
thorium oxide as disclosed in European patent application 0220343 A-1 and
Norwegian patent No. 178 958. The catalyst may exist in a fixed layer as
well as in a suspended form in the process.
Typical operation conditions for Fischer-Tropsch conversion are:
1. Total pressure of 5-80 bar, preferably 10-50 bar, particularly 20-40
bar,
2. Space velocity (the inverse of residence time): 100-20,000 vol.
(SPT)/vol.(cat)* hours, preferably 300-10,000, particularly 500-5000.
3. Temperature 160-300.degree. C., preferably 180-200.degree. C.,
particularly 200-240.degree. C.
4. Ratio H.sub.2 /CO (inlet) 1.0-3.0, preferably 1.5-2.5, particularly
1.7-2.1.
The produced synfuel is recovered as the product from the Fischer-Tropsch
reaction through the outlet 12. This synfuel will be subject to a further
refining process depending on the intended use, but this refining is not
considered part of the present invention and is not disclosed herein.
Fuel gas is recovered from the Fischer-Tropsch synthesis through the outlet
13. Part of this gas stream may be recycled to a conduit 15 to the
process, mixed with the preheated gas and together with this, passed to
the reforming reactor.
The residual part is passed through a pipe 14 and mixed with natural gas
fed through a conduit 32 to a gas power plant 30 which is simultaneously
supplied with fuel air through a pipe 31. On an annual basis the gas power
plant produces, by combustion of the mixture of natural gas and fuel gas
from the Fischer-Tropsch reactor, about 1800 MW, at the same time
supplying exhaust gas as previously mentioned for the preheating of the
natural gas to the reforming.
In the present embodiment the integrated plant further comprises a plant 40
comprising equipment for the preparation of liquefied natural gas (=LNG)
by compression and cooling of 4 giga standard m.sup.3 per year of natural
gas. Prior to condensing the natural gas to LNG, it is required to remove
CO.sub.2 from the gas to be condensed. This is performed in a CO.sub.2
elimination plant 45.
If the natural gas includes heavier components (NGL components such as
methane, propane, butane etc.), it may also be required, depending on the
amount and identity of such components, to separate such components from
the starting material being fed to the LNG plant 40. Such separation of
heavier components is performed in a NGL separation plant 47.
The separated CO.sub.2 and heavier components which are separated in the
NGL separation plant 47, are passed through conduit 46 and 48 respectively
together with the fed 8 to the preheating step 2 prior to the reformation.
A cryogenic process for the separation of air or preparation of nitrogen
(and which concomitantly will result in an oxygen enriched stream of air)
which can be used in the present air separation plant, is e.g. described
in the Norwegian publication for opposition No. 177728.
A process for the preparation of intermediate distillates in
Fischer-Tropsch synthesis with cobalt catalysts including parts of
zirconium, titanium and chromium, followed by a hydrogenation conversion
of the total synthesized products on a born noble-metal catalyst is
disclosed in the European patent application 0147873 A-1, and the
conditions for the preparation of methanol from synthesis gas, is e.g.
disclosed in the European patent application 0317035 A-2.
Particular benefits achieved by a plant according to the present invention
of the kind disclosed herein, is that an integrated plant for the
production of synfuel is obtained which, in addition to produce gas power
in considerably economical amount, also results in exhaust gas which may
be used for preheating the plant, the exhaust gas from the synfuel
production constituting part of the fuel for the gas power plant to obtain
a maximum utilization of products and side-products from this plant.
Such an integrated operation and such an integrated plant are, according to
the applicant's knowledge, not previously described and constitute a
valuable contribution to the field natural gas technology.
The inventive spirit is formulated in the appending claims. These are,
however, not meant to limit the invention, all equivalents residing within
the defined scope also having to be considered to constitute part of the
inventive spirit.
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